Reattachable introducer for a medical device deployment system

ABSTRACT

A reattachable introducer and method of using such introducer is disclosed for inserting an embolic coil deployment system into the tortuous vasculature of the human brain for placing an embolic coil within an aneurysm. The introducer includes a sheath having a lumen, a side opening and a longitudinal slit and includes a cylindrical sleeve slideably disposed about the sheath. A deployment catheter with a conical expander member is slideably disposed through the side opening of the sheath and through the lumen of the sheath. The conical expander member detaches the introducer from the deployment catheter through the longitudinal slit of the sheath, while the cylindrical sleeve reattaches the introducer to the deployment catheter through the longitudinal slit.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a reattachable introducer for insertinga medical device deployment system into the vasculature of a human bodyand further relates to a method of using such introducer. The deploymentsystem may be used for placing a medical device at a preselectedposition within a vessel. More particularly, the introducer is suitedfor inserting an embolic coil deployment system into the tortuousvasculature of the human brain for placing an embolic coil within ananeurysm.

[0003] 2. Description of the Prior Art

[0004] For many years physicians have been placing various deviceswithin a blood vessel of the human body in order to treat an aneurysm orto occlude a vessel. These devices are placed within the aneurysm orvessel using one of several different catheter deployment systems. Thesedeployment systems transport and release the devices at a particularlocation within the vessel. The combination of different devices anddifferent deployment systems provide physicians with reliable methods oftreating aneurysms.

[0005] Physicians place various types of devices within an aneurysm or avessel to occlude the flow of blood by promoting thrombus formation.Such devices include dilatation balloons, liquid medications, andembolic coils. Embolic coils may take the form of helically wound coils,randomly wound coils, coils wound within other coils, and many othercoil configurations. These coils are generally formed of radiopaquemetallic materials, such as platinum, gold, and tungsten, or alloys ofthese metals. Often times, several coils are placed at a given locationin order to occlude the flow of blood through the vessel.

[0006] U.S. Pat. No. 6,179,857, entitled, “Stretch Resistant EmbolicCoil With Variable Stiffness” discloses one example of such an emboliccoil design. The coil disclosed in this patent is a helically woundcoil, and various combinations of adjacent turns are spot weldedtogether to create a stretch resistant coil of varying flexibility. U.S.Pat. No. 6,183,491, entitled, “Embolic Coil Deployment System WithImproved Embolic Coil” discloses another embolic coil configurationwhich has a relatively flexible proximal portion which resistsstretching.

[0007] Also, U.S. Pat. No. 5,853,418, entitled “Stretch ResistantVaso-occlusive Coils,” discloses a helically wound coil having apolymeric stretch resistant member extending through the lumen of thecoil and fixedly attached to both the distal end and the proximal end ofthe coil. Other examples of coil configurations are disclosed in U.S.Pat. No. 5,334,210, entitled, “Vascular Occlusion Assembly” and U.S.Pat. No. 5,382,259 entitled, “Vasoocclusion Coil With Attached TubularWoven Or Braided Fibrous Covering.” With all such coil designs, it isimportant that the coils remain very flexible so that they may be passedthrough vessels with the use of a catheter deployment system.

[0008] A variety of coil deployment systems are available for placingembolic coils within an aneurysm or vessel. U.S. Pat. No. 6,113,622,entitled, “Embolic Coil Hydraulic Deployment System” and assigned to thesame assignee as the present patent application discloses one example ofsuch a deployment system. The hydraulic embolic coil deployment systemdisclosed in this patent uses fluid pressure which is applied to thelumen of the deployment catheter for expanding the distal sectionradially thereby releasing the embolic coil at a preselected position.

[0009] U.S. Pat. No. 5,350,397, entitled, “Axially Detachable EmbolicCoil Assembly” discloses another known coil deployment system whichutilizes a deployment catheter having a socket at the distal end forretaining a ball which is bonded to the proximal end of the emboliccoil. The ball is placed within the socket at the distal end of thedeployment catheter, and the deployment system is then moved into avessel to place the coil at a desired position. A pusher wire with apiston at its distal end is pushed distally from the proximal end of thedeployment catheter to thereby push the ball out of the socket andrelease the coil at the desired position.

[0010] Also, U.S. Pat. No. 5,263,964, entitled, “Coaxial TractionDetachment Apparatus and Method” discloses still another coil deploymentsystem. The system disclosed in this patent uses glue or solder forattaching an embolic coil to a guidewire which is, in turn, pushedthrough a flexible catheter for positioning the coil within the vesselat a preselected position. Once the coil is at the desired position, thecoil is restrained by the deployment catheter, and the guidewire ispulled from the proximal end of the coil causing the coil to becomedetached from the guidewire and released from the deployment system.

[0011] Additionally, U.S. patent application Ser. No. 09/580,684entitled, “Small Diameter Embolic Coil Hydraulic Deployment System,”filed on May 30, 2000 and assigned to the same assignee as the presentpatent application, discloses a vasoocclusive coil deployment system forplacing a small diameter coil. In the system disclosed in this patent,the distal end of a cylindrical headpiece is inserted into and bonded tothe embolic coil. The proximal end of the cylindrical headpiece has adiameter approximately equal to the diameter of the lumen of adeployment catheter so that the cylindrical headpiece is disposed influid-tight engagement with the lumen of the deployment catheter. Whenfluid pressure is applied to the lumen of the deployment catheter, theouter wall of the distal section of the deployment catheter expandsradially and releases the cylindrical headpiece along with the emboliccoil.

[0012] Examples of other such coil deployment systems are disclosed inU.S. Pat. No. 5,122,136, entitled, “Endovascular ElectrolyticallyDetachable Guidewire Tip For The Electroformation Of Thrombus InArteries, Veins, Aneurysms, Vascular Malformations And ArteriovenousFistulas” and U.S. Pat. No. 5,108,407, entitled, “Method And ApparatusFor Placement Of An Embolic Coil.”

SUMMARY OF THE INVENTION

[0013] In accordance with one aspect of the present invention, there isprovided an embolic coil deployment system and reattachable introducertherefor which includes a sheath which takes the form of an elongatedflexible tubular member having a lumen extending therethrough and havinga proximal end, a distal end and an outer wall. The sheath has a sideopening in the outer wall of the sheath adjacent to the proximal end ofthe sheath. The sheath also has a longitudinal slit extending throughthe outer wall of the sheath and extending from the side opening and ina direction toward the distal end of the sheath. The reattachableintroducer also includes a cylindrical sleeve which is slideablydisposed about the sheath and is movable between the side opening of thesheath and the distal end of the sheath. Furthermore, the embolic coildeployment system includes a deployment catheter having a lumenextending therethrough and having a proximal section and a distalsection. The deployment catheter is slideably disposed through the sideopening of the sheath and through the lumen of the sheath. Finally, theembolic coil deployment system includes a vascular occlusive emboliccoil being detachably attached to the distal section of the deploymentcatheter.

[0014] In accordance with another aspect of the present invention, thereis provided a reattachable introducer for use with an embolic coildeployment catheter to place an embolic coil into an aneurysm. Theintroducer includes a sheath which takes the form of an elongatedflexible tubular member having a lumen extending therethrough and havinga proximal end, a distal end and an outer wall. The sheath has a sideopening in the outer wall of the sheath adjacent to the proximal end ofthe sheath. The sheath also has a longitudinal slit extending throughthe outer wall of the sheath and extending from said side opening towardthe distal end of the sheath. The introducer further includes acylindrical sleeve which is slideably disposed about the sheath and ismovable between the side opening of the sheath and the distal end of thesheath.

[0015] In accordance with still another aspect of the present invention,there is provided a medical device deployment system and reattachableintroducer therefor which includes a sheath which takes the form of anelongated flexible tubular member having a lumen extending therethroughand having a proximal end, a distal end and an outer wall. The sheathhas a side opening in the outer wall of the sheath adjacent to proximalend of the sheath. The sheath also has a longitudinal slit extendingthrough the outer wall of the sheath and extending from the side openingand in a direction toward the distal end of the sheath. The reattachableintroducer also includes a cylindrical sleeve which is slideablydisposed about the sheath and is movable between the side opening of thesheath and the distal end of the sheath. Furthermore, the medical devicedeployment system includes a deployment catheter having a lumenextending therethrough and having a proximal section and a distalsection. The deployment catheter is slideably disposed through the sideopening of the sheath and through the lumen of the sheath. Finally, themedical device deployment system includes a medical device beingattached to the distal section of the deployment catheter.

[0016] In accordance with another aspect of the present invention, thedeployment catheter includes a conical expander member having a baseportion. The conical expander member tapers from the base portion toform a tip portion. The conical expander member is coaxially disposedabout the deployment catheter with the tip portion of the conicalexpander member extending distally from the base portion of the conicalexpander member so that as the deployment catheter is moved distally theexpander member causes the longitudinal slit to open thereby causing thesheath to separate from the deployment catheter.

[0017] In accordance with another aspect of the present invention, thesheath includes a sheath stop which takes the form of a projectiondisposed on the outer wall of the sheath at a position proximal to thedistal end of the sheath.

[0018] In accordance with still another aspect of the present invention,the sheath includes a sheath stop which takes the form of a cylindricalring having a lumen extending therethrough. The sheath stop is fixedlydisposed about the outer wall of the sheath at a position proximal tothe distal end of the sheath.

[0019] In accordance with yet another aspect of the present invention,the longitudinal slit of the sheath extends from the side opening to thesheath stop, and the deployment catheter includes a winged hub attachedto the proximal section of the deployment catheter.

[0020] In accordance with another aspect of the present invention, theside opening is generally circular and the side opening has a diametergreater than an outside diameter of the deployment catheter.

[0021] In accordance with still another aspect of the present invention,the side opening is generally oval in shape. The side opening has amajor axis and a minor axis. The major axis of the side opening isgenerally parallel with a longitudinal axis of the sheath. The minoraxis of the side opening is generally greater than an outside diameterof the deployment catheter.

[0022] In accordance with another aspect of the present invention, thereis provided a method for placing an embolic coil within an aneurysm orfor placing a medical device at a preselected position within a vessel.The method includes the step of providing a delivery catheter; areattachable introducer including a sheath having a lumen, a sideopening and a longitudinal slit; a cylindrical sleeve disposed about thesheath; a deployment catheter being slideably disposed through the sideopening of the sheath and through the lumen of the sheath; and avascular occlusive embolic coil or medical device being attached to thedistal section of the deployment catheter. The method also includes thestep of inserting the delivery catheter into the vasculature of the bodythen inserting the deployment catheter and introducer into a lumen ofthe delivery catheter.

[0023] Moreover, the method includes the step of sliding the cylindricalsleeve distally from the side opening of the sheath and toward thedistal end of the sheath. The method also includes the step of pushingthe deployment catheter distally through the side opening causing thesheath to detach from the deployment catheter through the longitudinalslit thereby causing the embolic coil or medical device to becomeexposed. The method further includes the step of releasing the emboliccoil within the aneurysm or the medical device at the preselectedposition then removing the deployment catheter and introducer. Finally,the method includes the step of removing the delivery catheter from thebody.

[0024] In accordance with still another aspect of the present invention,there is provided a method for retrieving a deployment catheter and anembolic coil or medical device from the body. The method includes thestep of providing a delivery catheter; a reattachable introducerincluding a sheath having a lumen, a side opening and a longitudinalslit; a cylindrical sleeve disposed about the sheath; a deploymentcatheter being slideably disposed through the side opening of the sheathand through the lumen of the sheath; and a vascular occlusive emboliccoil or medical device being attached to the distal section of thedeployment catheter. The method also includes the step of inserting thedelivery catheter into the vasculature of the body then inserting thedeployment catheter and introducer into a lumen of the deliverycatheter.

[0025] Moreover, the method includes the step of sliding the cylindricalsleeve distally from the side opening of the sheath and toward thedistal end of the sheath. The method also includes the step of pushingthe deployment catheter distally through the side opening causing thesheath to detach from the deployment catheter through the longitudinalslit thereby causing the embolic coil or medical device to becomeexposed. The method further includes the step of pulling the deploymentcatheter proximally thereby causing the embolic coil or medical deviceto become disposed within the lumen of the sheath then sliding thecylindrical sleeve proximally toward the side opening of the sheaththereby causing the sheath to reattach about the deployment catheterthrough the longitudinal slit and causing the sheath to pinch thedeployment catheter thereby preventing the sheath from sliding along thedeployment catheter. Finally, the method includes the step of removingthe deployment catheter, introducer and delivery catheter from the body.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is an enlarged perspective view of an embolic coildeployment system with an introducer disposed about a deploymentcatheter;

[0027]FIG. 2 is an enlarged, sectional view of the introducer inaccordance with the present invention;

[0028]FIG. 2a is an enlarged, cross-sectional view of the introducer ofFIG. 2 showing a longitudinal slit in an outer wall of the sheath;

[0029]FIG. 3 is an enlarged perspective view of the embolic coildeployment system and introducer showing the deployment catheter beingmoved distally, forcing the sheath off the deployment catheter andpushing an embolic coil out the end of the sheath; and,

[0030]FIG. 4 is an enlarged perspective view of the embolic coildeployment system and introducer showing the deployment catheter andcylindrical sleeve being moved proximally thereby pulling the emboliccoil back into the sheath and forcing the sheath back onto thedeployment catheter.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0031]FIG. 1 illustrates a deployment catheter 12, a reattachableintroducer 14, and an embolic coil 16. The deployment catheter 12 is anelongated tube with a lumen 18. Preferably, the proximal section 20 ofthe deployment catheter 12 is formed of a pellethane material having adurometer in a range of about 60D to 75D. The proximal section 20 issufficiently flexible to transverse the vasculature of the human body,but is sufficiently rigid so that it can be pushed distally through theintroducer 14. The distal section 22 of the deployment catheter 12 ispreferably formed of a pellethane material having a durometer of between25D and 55D with a durometer of 40D being the preferred durometer.

[0032] The deployment catheter 12 also includes a winged hub 24 coupledto the proximal section 20 of the deployment catheter 12. The winged hub24 may be made from plastic and aids in the insertion of the deploymentcatheter 12 into the vasculature of the body. Furthermore, thedeployment catheter 12 includes a conical expander member 25. Theconical expander member 25 is coaxially disposed about the deploymentcatheter 12 and tapers from its base portion 25 a to its tip portion 25b. The tip portion 25 b of the conical expander member 25 is distal thebase portion 25 a. The conical expander member 25 is preferably madefrom the same material as the winged hub 24. Finally, the deploymentcatheter 12 includes an embolic coil 16 attached to the distal section22 of the deployment catheter 12. The embolic coil 16 may take variousforms and configurations and may even take the form of a randomly woundcoil, however, a helically wound flexible embolic coil is illustrated inFIG. 1.

[0033]FIG. 2 illustrates the introducer 14 which includes a sheath 26which is approximately 80 centimeters in length and is formed of apolymer material with a durometer in the range of about 50D and 80D. Thesheath 26 has a diameter of approximately 0.1 centimeters, and the lumen28 of the sheath 26 has a diameter slightly greater than an outsidediameter of the deployment catheter 12. The sheath 26 includes a sideopening 30 adjacent to the proximal end 32 of the sheath 26. The sideopening 30 is a hole cut in the outer wall 34 of the sheath 26 andextends through the outer wall 34 and into the lumen 28 of the sheath26. The side opening 30 may take the form of a circle cut through theouter wall 34 of the sheath 26 or may take other configurations, like anoval. Preferably, the side opening 30 has a diameter in the range ofabout 0.23 centimeters to 0.38 centimeters. The sheath 26 also includesa longitudinal slit 36 in the outer wall 34 of the sheath 26. Thelongitudinal slit 36 is approximately 60 centimeters in length andextends from the side opening 30 and in a direction toward the distalend 37 of the sheath 26.

[0034] The introducer 14 also includes a sheath stop 38 which isdisposed about the outer wall 34 of the sheath 26 at a position proximalto the distal end 37 of the sheath 26. The sheath stop 38 is cylindricalin shape and is made of nylon but may also be formed from plastic or apolymer. The length of the sheath stop 38 is approximately 1.3centimeters while the preferred diameter of the sheath stop 38 is 0.18centimeters. A cylindrical sleeve 40 is slideably disposed about thesheath 26 and is approximately 4.5 centimeters in length. Thecylindrical sleeve 40 is generally cylindrical in shape and has a lumen42. The cylindrical sleeve 40 is formed of polyethylene but may also bemade from plastic or a polymer. The lumen 42 of the cylindrical sleeve40 has a diameter slightly greater than the outside diameter of thesheath 26. Preferably, the outside diameter of the cylindrical sleeve 40is 0.18 centimeters.

[0035]FIG. 2A illustrates a cross sectioned view of the sheath 26between the side opening 30 and the cylindrical sleeve 40. Thelongitudinal slit 36 runs through the outer wall 34 of the sheath 26 andinto the lumen 28 of the sheath 26. The cylindrical sleeve 40 isslideably disposed about the sheath 26.

[0036]FIG. 3 illustrates the winged hub 24, conical expander member 25and deployment catheter 12 being moved distally through the side opening30 of the sheath 26, forcing the sheath 26 to separate from thedeployment catheter 12 through the longitudinal slit 36 and pushing theembolic coil 16 out the distal end 37 of the sheath 26.

[0037]FIG. 4 illustrates the winged hub 24, conical expander member 25and deployment catheter 12 being moved proximally, pulling the emboliccoil 16 back into the distal end 37 of the sheath 26. The cylindricalsleeve 40 is moved proximally over the sheath 26 causing the sheath26.to reattach about the deployment catheter 12 through the longitudinalslit 36.

[0038] The introducer operates to place an embolic coil into an aneurysmof the brain. With the introducer slideably disposed over a deploymentcatheter, the cylindrical sleeve is positioned generally over the sideopening causing the introducer to be pinched to the deployment catheter.In this configuration, the deployment catheter and introducer can beinserted into a delivery catheter. The sheath of the introducer protectsan embolic coil as the distal section of the deployment catheter isinserted into the patient. The deployment catheter and introducer areinserted until the sheath stop generally reaches the proximal end of thedelivery catheter. At this point, the cylindrical sleeve is moveddistally to expose the side opening. Then, the deployment catheter ismoved distally causing the conical expander member to move distally andforcing the sheath off the deployment catheter. The sheath allows thedeployment catheter to enter the vasculature more easily; otherwise, theflexible deployment catheter would bend as it was being pushed distally.At the same time the sheath is separating from the deployment catheter,the embolic coil attached to the distal section of the deploymentcatheter exits the sheath.

[0039] From this position, the physician can deploy the embolic coil ata preselected position within a vessel. Once the coil is no longerattached to the deployment catheter, the deployment catheter andintroducer are removed from the vasculature and another deploymentcatheter and introducer are introduced in the same manner when morecoils are required.

[0040] If, before the embolic coil is deployed, the physician decides toretrieve the coil, the sheath can be reattached, and the system can bereused. To do this, the deployment catheter is pulled proximally untilthe embolic coil is again disposed within the sheath. Then, thecylindrical sleeve is slid proximally, reattaching the sheath onto thedeployment catheter through the longitudinal slit. The cylindricalsleeve is then slid generally over the side opening to hold the sheathto the deployment catheter. Finally, the deployment catheter andintroducer are removed from the patient.

[0041] A novel system has been disclosed in which an introducer is usedto introduce an embolic coil deployment system into the vasculature ofthe body. Although a preferred embodiment of the invention has beendescribed, it is to be understood that various modifications may be madeby those skilled in the art without departing from the scope of thepresent invention. For example, there are many variations andmodifications of the embolic coil, including numerous coil windingconfigurations, or alternatively, other types of vascular occlusivedevices may be utilized, such as dilation balloons, radiopaque fluids,and liquid medications.

[0042] These and other modifications would be apparent to those havingordinary skill in the art to which this invention relates and areintended to be within the scope of the claims which follow.

That which is claimed is:
 1. An embolic coil deployment system andreattachable introducer therefor comprising: a sheath which takes theform of an elongated flexible tubular member having a lumen extendingtherethrough and having a proximal end, a distal end and an outer wall,said sheath having a side opening in the outer wall of said sheathadjacent to the proximal end of said sheath, and said sheath having alongitudinal slit extending through the outer wall of said sheath andextending from said side opening and in a direction toward the distalend of said sheath; a cylindrical sleeve slideably disposed about saidsheath and being movable between said side opening of said sheath andthe distal end of said sheath; a deployment catheter having a lumenextending therethrough and having a proximal section and a distalsection, said deployment catheter being slideably disposed through saidside opening of said sheath and through the lumen of said sheath; and, avascular occlusive embolic coil being detachably attached to the distalsection of said deployment catheter.
 2. An embolic coil deploymentsystem and a reattachable introducer therefor as defined in claim 1,wherein said deployment catheter includes a conical expander memberhaving a base portion, said conical expander member tapers from saidbase portion to form a tip portion, said conical expander member beingcoaxially disposed about said deployment catheter with the tip portionof said conical expander member extending distally from the base portionof said conical expander member so that as said deployment catheter ismoved distally said expander member causes said longitudinal slit toopen thereby causing said sheath to separate from said deploymentcatheter.
 3. An embolic coil deployment system and a reattachableintroducer therefor as defined in claim 1, wherein said sheath includesa sheath stop which takes the form of a cylindrical ring having a lumenextending therethrough, said sheath stop being fixedly disposed aboutthe outer wall of said sheath at a position proximal to the distal endof said sheath.
 4. An embolic coil deployment system and a reattachableintroducer therefor as defined in claim 2, wherein said sheath includesa sheath stop which takes the form of a cylindrical ring having a lumenextending therethrough, said sheath stop being fixedly disposed aboutthe outer wall of said sheath at a position proximal to the distal endof said sheath.
 5. An embolic coil deployment system and a reattachableintroducer therefor as defined in claim 3, wherein said longitudinalslit of said sheath extends from said side opening to said sheath stop.6. An embolic coil deployment system and a reattachable introducertherefor as defined in claim 4, wherein said longitudinal slit of saidsheath extends from said side opening to said sheath stop.
 7. Areattachable introducer for use with an embolic coil deployment catheterto place an embolic coil into an aneurysm, said introducer comprising: asheath which takes the form of an elongated flexible tubular memberhaving a lumen extending therethrough and having a proximal end, adistal end and an outer wall, said sheath having a side opening in theouter wall of said sheath adjacent to the proximal end of said sheath,said sheath having a longitudinal slit extending through the outer wallof said sheath and extending from said side opening toward the distalend of said sheath; and, a cylindrical sleeve slideably disposed aboutsaid sheath and being movable between said side opening of said sheathand the distal end of said sheath;
 8. A reattachable introducer asdefined in claim 7, wherein said sheath includes a sheath stop whichtakes the form of a cylindrical ring having a lumen extendingtherethrough, said sheath stop being fixedly disposed about the outerwall of said sheath at a position proximal to the distal end of saidsheath.
 9. A reattachable introducer as defined in claim 8, wherein saidlongitudinal slit of said sheath extends from said side opening to saidsheath stop.
 10. A medical device deployment system and a reattachableintroducer therefor comprising: a sheath which takes the form of anelongated flexible tubular member having a lumen extending therethroughand having a proximal end, a distal end and an outer wall, said sheathhaving a side opening in the outer wall of said sheath adjacent to theproximal end of said sheath, and said sheath having a longitudinal slitextending through the outer wall of said sheath and extending from saidside opening and in a direction toward the distal end of said sheath; acylindrical sleeve slideably disposed about said sheath and beingmovable between said side opening of said sheath and the distal end ofsaid sheath; a deployment catheter having a lumen extending therethroughand having a proximal section and a distal section, said deploymentcatheter being slideably disposed through the side opening of saidsheath and through the lumen of said sheath; and, a medical device beingdetachably attached to the distal section of said deployment catheter.11. A medical device deployment system and a reattachable introducertherefor as defined in claim 10, wherein said deployment catheterincludes a conical expander member having a base portion, said conicalexpander member tapers from said base portion to form a tip portion,said conical expander member being coaxially disposed about saiddeployment catheter with the tip portion of said conical expander memberextending distally from the base portion of said conical expander memberso that as said deployment catheter is moved distally said expandermember causes said longitudinal slit to open thereby causing said sheathto separate from said deployment catheter.
 12. A medical devicedeployment system and a reattachable introducer therefor as defined inclaim 10, wherein said sheath includes a sheath stop which takes theform of a cylindrical ring having a lumen extending therethrough, saidsheath stop being fixedly disposed about the outer wall of said sheathat a position proximal to the distal end of said sheath.
 13. A medicaldevice deployment system and a reattachable introducer therefor asdefined in claim 10, wherein said deployment catheter includes a wingedhub attached to the proximal section of said deployment catheter.
 14. Amedical device deployment system and a reattachable introducer thereforas defined in claim 10, wherein said side opening is generally circularand said side opening has a diameter greater than an outside diameter ofsaid deployment catheter.
 15. A medical device deployment system and areattachable introducer therefor as defined in claim 10, wherein saidside opening is generally oval in shape, said side opening having amajor axis and a minor axis, said major axis of said side opening beinggenerally parallel with a longitudinal axis of said sheath, said minoraxis of said side opening being generally greater than an outsidediameter of said deployment catheter.
 16. A medical device deploymentsystem and a reattachable introducer therefor as defined in claim 11,wherein said sheath includes a sheath stop which takes the form of acylindrical ring having a lumen extending therethrough, said sheath stopbeing fixedly disposed about the outer wall of said sheath at a positionproximal to the distal end of said sheath.
 17. A medical devicedeployment system and a reattachable introducer therefor as defined inclaim 11, wherein said deployment catheter includes a winged hubattached to the proximal section of said deployment catheter.
 18. Amedical device deployment system and a reattachable introducer thereforas defined in claim 11, wherein said side opening generally takes theform of a circle, said side opening having a diameter generally greaterthan an outside diameter of said deployment catheter.
 19. A medicaldevice deployment system and a reattachable introducer therefor asdefined in claim 11, wherein said side opening generally takes the formof an oval, said side opening having a major axis and a minor axis, saidmajor axis of said side opening being generally parallel with alongitudinal axis of said sheath, said minor axis of said side openingbeing generally greater than an outside diameter of said deploymentcatheter.
 20. A medical device deployment system and a reattachableintroducer therefor as defined in claim 12, wherein said longitudinalslit of said sheath extends from said side opening to said sheath stop.21. A medical device deployment system and a reattachable introducertherefor as defined in claim 16, wherein said longitudinal slit of saidsheath extends from said side opening to said sheath stop.
 22. Areattachable introducer for use with a medical device deploymentcatheter to place a medical device at a preselected position within avessel, said reattachable introducer comprising: a sheath which takesthe form of an elongated flexible tubular member having a lumenextending therethrough and having a proximal end, a distal end and anouter wall, said sheath having a side opening in the outer wall of saidsheath adjacent to the proximal end of said sheath, said sheath having alongitudinal slit extending through the outer wall of said sheath andextending from said side opening toward the distal end of said sheath;and, a cylindrical sleeve slideably disposed about said sheath and beingmovable between said side opening of said sheath and the distal end ofsaid sheath.
 23. A reattachable introducer as defined in claim 22,wherein said sheath includes a sheath stop which takes the form of aprojection disposed on the outer wall of said sheath at a positionproximal to the distal end of said sheath.
 24. A reattachable introduceras defined in claim 23, wherein said sheath includes a sheath stop whichtakes the form of a cylindrical ring having a lumen extendingtherethrough, said sheath stop being fixedly disposed about the outerwall of said sheath at a position proximal to the distal end of saidsheath.
 25. A reattachable introducer as defined in claim 23, whereinsaid longitudinal slit of said sheath extends from said side opening tosaid sheath stop.
 26. A reattachable introducer as defined in claim 24,wherein said longitudinal slit of said sheath extends from said sideopening to said sheath stop.
 27. A method for placing an embolic coilwithin an aneurysm, said method comprising the steps of: providing adelivery catheter; a reattachable introducer including a sheath having alumen, a side opening and a longitudinal slit and including acylindrical sleeve slideably disposed about said sheath; a deploymentcatheter being slideably disposed through the side opening of saidsheath and through the lumen of said sheath; and a vascular occlusiveembolic coil being detachably attached to a distal section of saiddeployment catheter; inserting said delivery catheter into a vessel ofthe body; inserting said deployment catheter and said introducer into alumen of said delivery catheter; sliding said cylindrical sleevedistally from said side opening of said sheath and toward the distal endof said sheath; pushing said deployment catheter distally through saidside opening causing said sheath to detach from said deployment catheterthrough said longitudinal slit thereby causing said embolic coil tobecome exposed; releasing said embolic coil within the aneurysm;removing said deployment catheter and said introducer; and, removingsaid delivery catheter from the body.
 28. A method for retrieving adeployment catheter and an embolic coil from the body, said methodcomprising the steps of: providing a delivery catheter; a reattachableintroducer including a sheath having a lumen, a side opening and alongitudinal slit and including a cylindrical sleeve slideably disposedabout said sheath; a deployment catheter being slideably disposedthrough the side opening of said sheath and through the lumen of saidsheath; and a vascular occlusive embolic coil being detachably attachedto a distal section of said deployment catheter; inserting said deliverycatheter into a vessel of the body; inserting said deployment catheterand said introducer into a lumen of said delivery catheter; sliding saidcylindrical sleeve distally from said side opening of said sheath andtoward the distal end of said sheath; pushing said deployment catheterdistally through said side opening causing said sheath to detach fromsaid deployment catheter through said longitudinal slit thereby causingsaid embolic coil to become exposed; pulling said deployment catheterproximally thereby causing said embolic coil to become disposed withinthe lumen of said sheath; sliding said sleeve proximally toward the sideopening of said sheath thereby causing said sheath to reattach aboutsaid deployment catheter through said longitudinal slit and causing saidsheath to pinch said deployment catheter thereby preventing said sheathfrom sliding along said deployment catheter; removing said deploymentcatheter and said introducer; and, removing said delivery catheter fromthe body.
 29. A method for placing a medical device at a preselectedposition within a vessel, said method comprising the steps of: providinga delivery catheter; a reattachable introducer including a sheath havinga lumen, a side opening and a longitudinal slit and including acylindrical sleeve slideably disposed about said sheath; a deploymentcatheter being slideably disposed through the side opening of saidsheath and through the lumen of said sheath; and a medical device beingdetachably attached to a distal section of said deployment catheter;inserting said delivery catheter into a vessel of the body; insertingsaid deployment catheter and said introducer into a lumen of saiddelivery catheter; sliding said cylindrical sleeve distally from saidside opening of said sheath and toward the distal end of said sheath;pushing said deployment catheter distally through said side openingcausing said sheath to detach from said deployment catheter through saidlongitudinal slit thereby causing said medical device to become exposed;releasing said medical device at the preselected position within thevessel; removing said deployment catheter and said introducer; and,removing said delivery catheter from the body.
 30. A method forretrieving a deployment catheter and a medical device from the body,said method comprising the steps of: providing a delivery catheter; areattachable introducer including a sheath having a lumen, a sideopening and a longitudinal slit and including a cylindrical sleeveslideably disposed about said sheath; a deployment catheter beingslideably disposed through the side opening of said sheath and throughthe lumen of said sheath; and a medical device being detachably attachedto a distal section of said deployment catheter; inserting said deliverycatheter into a vessel of the body; inserting said deployment catheterand said introducer into a lumen of said delivery catheter; sliding saidcylindrical sleeve distally from said side opening of said sheath andtoward the distal end of said sheath; pushing said deployment catheterdistally through said side opening causing said sheath to detach fromsaid deployment catheter through said longitudinal slit thereby causingsaid medical device to become exposed; pulling said deployment catheterproximally thereby causing said medical device to become disposed withinthe lumen of said sheath; sliding said sleeve proximally toward the sideopening of said sheath thereby causing said sheath to reattach aboutsaid deployment catheter through said longitudinal slit and causing saidsheath to pinch said deployment catheter thereby preventing said sheathfrom sliding along said deployment catheter; removing said deploymentcatheter and said introducer; and, removing said delivery catheter fromthe body.